Apparatus for treating plastic sheets



Jan. 14, 1969 H, MlLLER ET AL 3,421,180

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1561/1141 1/0 and diam/Madam United States Patent 3 421,180 APPARATUSFOR TliEATING PLASTIC SHEETS Alfred H. Miller, Glenn Perry and LawrenceC. Wheat, Toledo, Ohio, assignors to Libbey-Owens-Ford Glass Company,Toledo, Ohio, a corporation of Ohio Original application Oct. 21, 1964,Ser. No. 405,383, now Patent No. 3,341,889. Divided and this applicationJuly 18, 1967, Ser. No. 705,234 US. Cl. 18-4 6 Claims Int. Cl. B29c3/00; F27b 9/14; F27b 9/12 ABSTRACT OF THE DISCLOSURE Apparatus fortreating plastic sheets, comprising an elongated heating oven and anelongated cooling tunnel above said heating oven and having its entranceend communicating with the exit end of the heating oven, with means forsupporting and conveying the sheets in a ventical position successivelythrough said heating oven and cooling tunnel, cooled dry air beingintroduced into the cooling tunnel from which it passes into the heatingoven where it is dried and heated and then recirculated through saidheating oven.

The present invention relates generally to the manufacture ofglare-reducing windows, or the like and more particularly to an improvedapparatus for shaping the plastic interlayer for curved or bentlaminated safety glass Windshields or windows when said interlayer isprovided with a glare-reducing portion.

This application is a division of application Ser. No. 405,383, filedOct. 21, 1964 and now Patent No. 3,341,889.

In shaping the plastic interlayers for laminated safety glassWindshields or windows it has been customary to first cut a. continuouslength or roll of plastic into individual sheets, and then clamp eachindividual sheet along two opposite edges only in a frame to hold it inits normal shape. T ractive forces are then applied to the lowerunsupported edge of the sheet while supporting the frame and sheet in avertical position and simultaneously heating the sheet until it has beenstretched or shaped in the desired manner. After heating, the sheet iscooled to retain its desired shape. It has heretofore been the practiceto clamp only a single sheet of plastic in a frame, with a plurality ofsuch frames being hung in a vertical position on a rack or truck whichis then passed first into a heating chamber and subsequently into acooling chamber.

While the invention is applicable to the shaping of individual plasticsheets supported in separate frames, it is of particular utility where aplurality of continuous lengths of thermoplastic material are withdrawnfrom separate sources of supply and, while superimposed one upon theother, are clamped at their free ends in a frame and uniformly stretchedor placed in tension. While maintained in tension, the continuouslengths of plastic are also clamped in the frame at a point remote fromthe free ends thereof and then cut transversely from the continuouslengths outwardly of the frame to provide a plurality of individualsheets. A succession of frames, each with a plurality of uniformly tautor tensioned sheets clamped therein, are supported in vertical positionand moved in spaced relation first through a heating zone and thenthrough a cooling zone. During the heating of the sheets, tractiveforces applied to the lower unsupported edges thereof cause said sheetsto be stretched or distorted in the plane of the sheets to the desiredcurvature or shape.

As herein provided, the air in both the heating zone and cooling zone ismaintained within desired ranges of ICC Working temperatures whereby theplastic sheets will become shaped while heat-softened and then set inthe desired curvature to which they were shaped as they are cooled. Toobtain gradual drying of the sheets as they cool, conditioned air issupplied to the cooling zone and as the frames reach the exit end ofsaid cooling Zone, they are successively conveyed with the shaped sheetsinto a room of closely controlled temperature and humidity to obivatethe tendency of the plastic to relax, due to its elastic memory, fromthe curvature to which it was shaped. The plastic sheets aremaintainedunder such controlled conditions until assembled with the glass sheetsin the manufacture of laminated safety glass.

It is therefore a primary object of the present invention to provide animproved apparatus for shaping sheets of plastic material employed asthe interlayer in the production of curved or bent laminated safetyglass windows or Windshields having a glare-reducing area in asubstantially continuous manner.

Another object of the invention is to provide an apparatus for shapingplastic sheets having a colored band along and parallel to one marginaledge of the sheet, in which a substantially continuous length of plasticmaterial is withdrawn from a source of supply and clamped at the freeend thereof in one end of a frame and also clamped at a point remotefrom said free end in the opposite end of said frame, the plastic beingthen cut transversely outwardly of the frame to form an individual sheetof predetermined size, the frame with the sheet clamped therein beinghung in a vertical position with the colored band at the upper edgethereof, and tractive forces being applied to the lower edge of thesheet and in the plane of the sheet and the sheet then heated to causeit to be deflected downwardly resulting in the up per and lowerlongitudinal edges thereof being curved in the same direction afterwhich the sheet is cooled.

Another object of the invention is to provide such an apparatus whereina plurality of substantially continuous lengths of plastic material aredrawn from a plurality of sources of supply and sections ofpredetermined length transversely clamped in a frame along two spacedlines in such a manner as to place the clamped sections under uniformtension, after which the continuous lengths of plastic are cuttransversely outwardly of the frame to provide individual sheets whichare shaped in the above manner. 7

Another object of the invention is to provide such an apparatus in whichthe substantially continuous lengths of plastic material are drawn fromthe sources of supply in superimposed contacting relation between a pairof feed rolls and the free ends thereof clamped together, after whichthe feed rolls are moved outwardly to place the plastic material undertension, the plastic material being then clamped inwardly of the freeends thereof to provide uniformly taut sections of predetermined lengthbefore the continuous lengths of plastic are cut to form individualsheets.

A further object of the invention is to provide such an apparatus inwhich the plurality of substantially continuous lengths of plasticmaterial after being drawn from their separate sources of supply andbefore passing between the feed rolls are permitted, while hanging infreely suspended loops, to relax and obtain a uniformity of linealtension prior to their being clamped in a frame and cut into individualsheets.

A further object of the invention is to provide such an apparatus inwhich a plurality of frames, each having a plurality of plastic sheetsclamped therein, are hung in a vertical position and moved substantiallycontinuously in spaced relation to one another through a zone ofcontrolled humidity and heated air to cause the plurality of sheets tobe shaped by downward deflection and then passed through a zone ofcontrolled humidity and cooling air to set the shaped curvature thereinafter which the sheets are removed from each of the frames for storagein a room having controlled temperature and humidity.

Other objects and advantages of the invention will become more apparentduring the course of the following description when read in connectionwith the accompanying drawings.

In the drawings, wherein like numerals are employed to designate likeparts throughout the same:

FIG. 1 is a perspective view of a windshield, produced in accordancewith this invention, shown in its functional position in the windshieldopening of an automobile;

FIG. 2 is a front elevation of the windshield;

FIG. 3 is a transverse vertical sectional view taken on the line 33 ofFIG. 2;

FIG. 4 is a front elevation of a support frame for distortion ofthermoplastic sheets in accordance with the invention;

FIG. 5 is an end elevation of the support frame;

FIG. 6 is a longitudinal vertical section taken on line 6-6 of FIG. 5;

FIG. 7 is a transverse vertical section taken on line 77 of FIG. 4;

FIG. 8 is a horizontal section taken on line 8-8 of FIG. 4;

FIG. 9 is an enlarged detail view of a clamping member of the supportframe; V

FIG. 10 is a schematic side elevation of a continuous distortionapparatus constructed in accordance with the invention;

FIG. 11 is an enlarged longitudinal vertical section of one end of theapparatus;

FIG. 12 is a transverse vertical section taken on line 12-12 of FIG. 10;

FIG. 13 is a horizontal section taken on line 13-13 of FIG. 11;

FIG. 14 is a horizontal section of a roll stand and taken on line 14-14of FIG. 12;

FIG. 15 is a fragmentary view of the upper end of a thermoplasticsheeting feeder unit;

FIG. 16 is a horizontal section taken on line 16-16 of FIG. 15;

FIG. 17 is a transverse vertical section taken on line 17-17 of FIG. 15,and illustrates the upper end of the feeder unit;

FIG. 18 is a detail view at the lower end of the feeder unit;

FIG. 19 is a fragmentary perspective view of one form of conveyor chainand of a support track on which the same is supported;

FIG. 20 is a plan view of an assembly and stretching unit;

FIG. 21 is an enlarged fragmentary side elevation of the assembly unit;

FIG. 22 is a view of one end of the assembly unit;

FIG. 23 is a similar view of the opposite end of the unit;

FIG. 24 is a longitudinal vertical section of the unit and as taken online 24-24 of FIG. 22;

FIG. 25 is a longitudinal section taken on line 25-25 of FIG. 23;

FIG. 26 is a horizontal section taken on line 26-26 of FIG. 22;

FIG. 27 is a transverse vertical section takenon line 27-27 of FIG. 24;

FIG. 28 is a transverse vertical section taken on line 28-28 of FIG. 25;

FIG. 29 is a transverse vertical section taken on line 29-29 of FIG. 22;

FIG. 30 is an enlarged detail view taken on line 30-30 of FIG. 20;

FIG. 31 is an enlarged detail view taken on line 31-31 of FIG. 20;

FIG. 32 is a fragmentray elevatiQil Of a tension control device;

FIG. 33 is a perspective view of the frame structure of the assembly andstretching unit;

FIG. 34 is a perspective view of a clamp and traction element;

FIG. 35 is a longitudinal vertical section of the entry end of theheating oven;

FIG. 36 is a fragmentary plan view illustrating latching means forlocating the frames in spaced order within the heating oven;

FIG. 37 is a side elevation of the latching means;

FIG. 38 is a plan view of the latching means;

FIG. 39 is a transverse vertical section of one transfer area of theapparatus as taken on line 39-39 of FIG. 10;

FIG. 40 is a longitudinal vertical section taken on line 40-40 of FIG.39;

FIG. 41 is a horizontal section taken on line 41-41 of FIG. 39;

FIG. 42 is a horizontal section taken on line 42-42 of FIG. 39;

FIG. 43 is a fragmentary detail view;

FIG. 44 is a perspective view of a conveyor chain support member;

FIG. 45 is a detail view of a part of the conveyor systems;

FIG. 46 is an end elevation of a second transfer area of the apparatus;

FIG. 47 is a longitudinal vertical section'taken on line 47-47 of FIG.46;

FIG. 48 is a horizontal section taken on line 48-48 of FIG. 47;

FIG. 49 is a transverse vertical section taken on line 49-49 of FIG. 48;

FIG. 50 is an enlarged horizontal section taken on line 50-50 of FIG.47;

FIGS. 5156 are a series of views illustrating the sequential stepscarried out in the assembly of thermoplastic sheets on a support frame;and

FIG. 57 is a front elevation of a windshield embodying a modified formof the invention.

In FIG. 1 of the drawings, there is shown a windshield 10 as it appearsfrom the outside of the automobile 11 in which the windshield ismounted. The windshield 10 is of a conventional laminated glassconstruction in that it comprises (FIG. 3) two sheets of glass 12 and 13and a non-brittle plastic interlayer 14 such as poly-vinyl butyralresin, interposed therebetween. The windshield 10 of FIG. 1, or a shownin plan in FIG. 2 includes a glarereducing area 15 which is a neutralshading within the windshield itself and is vignetted or graduated inshade from a deep or dark hue as at 16, along the upper margin of thewindshield, which may be opaque, or nearly opaque, to a very light hueas at 17, in the area adjacent the essentially transparent viewing area18 through which the driver clearly sees the road and approachingtraffic. The utility and advantages of the glare-reducing area or bandare of course immediately apparent and presently well-known to themotoring public as well as those skilled in the art. Thus, the depth ofhue or color, and consequently the glare-reducing properties, are mostintense in the upper area of the windshield from which the most glarewill come, and lightest in the area where maximum'transparency orvisibility is required. Stated otherwise, the amount of light reachingthe eyes of the driver is gradually increased as he shifts the line ofhis sight downwardly toward the area where complete visibility isessential and, conversely, the amount of light reaching his eyes will beprogressively decreased as he moves the line of his sight upwardlytoward the area of potentially greatest glare.

It is further known that the lowermost limit or fadeolf line of theglare-reducing area or band should be horizontal and substantiallyparallel to the horizon when the windshield is installed in itsfunctional position in an automobile. Due to the angle at which thewindshield is installed and additionally the curvature to which the

